In a printed-wiring board on which an electronic component has been mounted, such a heat problem that a temperature of the electronic component (semiconductor package such as an IC, LSI, or the like) rises occurs. This is because a driving ability of the electronic component has been enhanced. Therefore, an electronic component such as a semiconductor package (Heat_Quad_Flat_Non_lead_package: hereinbelow, referred to as HQFN) having terminal groups arranged on four sides of a bottom surface and a heat radiation plate serving as a heat radiation part for heat radiation arranged on the inside of the terminal groups, or the like has been produced.
The heat radiation plate of electronic component is joined with a land for heat radiation of the printed-wiring board by a conductive jointing material such as a solder or the like. Thus, a heat generated in the electronic component is radiated from the heat radiation plate to the land for heat radiation of the printed-wiring board through the jointing material. By a via conductor connected to the land for heat radiation, the heat is radiated to a layer on the side opposite to a layer on which the electronic component has been mounted or to a conductor pattern arranged in a layer existing at an intermediate position between the electronic component mounted layer and the layer on the opposite side.
However, an amount of processes per unit time of the electronic component increases and there is such a tendency that in association with an increase in power loss (electric power consumption) per unit time, the temperature of the electronic component also rises.
As a conventional technology for solving such a heat problem, such a technology that a fan-shaped projecting portion which projects from a land for a heat radiation plate toward the outside of an electronic component is formed and a heat generated in the electronic component is radiated from the projecting portion has been proposed (refer to Patent Literature 1).